From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org,
Masami Hiramatsu <mhiramat@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [v2, 3/4] powerpc/kprobes_on_ftrace: Skip livepatch_handler() for jprobes
Date: Mon, 19 Jun 2017 22:22:40 +1000 (AEST) [thread overview]
Message-ID: <3wrqqh0yNKz9s89@ozlabs.org> (raw)
In-Reply-To: <354168131ffd13a9109172f616255fe1e0983387.1496309487.git.naveen.n.rao@linux.vnet.ibm.com>
On Thu, 2017-06-01 at 10:48:17 UTC, "Naveen N. Rao" wrote:
> ftrace_caller() depends on a modified regs->nip to detect if a certain
> function has been livepatched. However, with KPROBES_ON_FTRACE, it is
> possible for regs->nip to have been modified by the kprobes pre_handler
> (jprobes, for instance). In this case, we do not want to invoke the
> livepatch_handler so as not to consume the livepatch stack.
>
> To distinguish between the two (kprobes and livepatch), we check if
> there is an active kprobe on the current function. If there is, then we
> know for sure that it must have modified the NIP as we don't support
> livepatching a kprobe'd function. In this case, we simply skip the
> livepatch_handler and branch to the new NIP. Otherwise, the
> livepatch_handler is invoked.
>
> Fixes: ead514d5fb30a ("powerpc/kprobes: Add support for
> KPROBES_ON_FTRACE")
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/c05b8c4474c03026aaa7f8872e7836
cheers
next prev parent reply other threads:[~2017-06-19 12:22 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-01 10:48 [PATCH v2 0/4] ftrace/kprobe fixes Naveen N. Rao
2017-06-01 10:48 ` [PATCH v2 1/4] powerpc/kprobes: Pause function_graph tracing during jprobes handling Naveen N. Rao
2017-06-08 13:43 ` Masami Hiramatsu
2017-06-08 15:33 ` Steven Rostedt
2017-06-19 12:22 ` [v2, " Michael Ellerman
2017-06-01 10:48 ` [PATCH v2 2/4] powerpc/ftrace: Pass the correct stack pointer for DYNAMIC_FTRACE_WITH_REGS Naveen N. Rao
2017-06-19 12:22 ` [v2, " Michael Ellerman
2017-06-01 10:48 ` [PATCH v2 3/4] powerpc/kprobes_on_ftrace: Skip livepatch_handler() for jprobes Naveen N. Rao
2017-06-08 13:59 ` Masami Hiramatsu
2017-06-15 11:19 ` Michael Ellerman
2017-06-15 15:32 ` Naveen N. Rao
2017-06-19 12:22 ` Michael Ellerman [this message]
2017-06-01 10:48 ` [PATCH v2 4/4] powerpc/xmon: Disable ftrace while in xmon Naveen N. Rao
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